Viscous Fan's ?????

Hi all,

The Viscous unit for my 90 2.5TD is knackered. Does anybody know if it is possible to get these reconditioned, or where to buy reconditioned units????

I have had some bad luck with second hand ones, and a new one is in the region of =A355.00.

Cheers,

Andy

The Viscous unit for my 90 2.5TD is knackered. Does anybody know if it is possible to get these reconditioned, or where to buy reconditioned units????

I have had some bad luck with second hand ones, and a new one is in the region of £55.00.

Sorry, I don't think they can be reconditioned. In all honesty, they are very reliable bits of kit, I happily remove electric kits and fit viscous fans back on, they keep the engine more stable, thermally, than any electric does. Fit a new one, it'll probably outlast the engine and chassis. Badger.

I agree with Badger, replace it with another.

That said, how do you know its broken? Is it in pieces or are you assuming its broken because you can still spin it freely when the engine is at running temp (In the UK this is normal behaviour as they tend not to run hot enough to solidify (for the want of a better word) the viscous fluid? When the engine is first started from cold it should blow a gale over the engine and then 30s or a minute later you should feel the air flow reduce. If it behaves like that when cold, I believe it should be OK.

Jon

i take it that its knackered, as when i start the engine from cold, or the engine is at normal running temeperature, and idling or fast running, i canot feel any air being pulled from the fan, and you can see the fan spinning, but very slowly.

i have fitted the blades to an old seized viscouse i hapened to have laying around, and i have "a gale" blowing over the engine.

Andy

Defo change for another then... Or save £60 and use the seized one as a permenant fixture... I would. A permenent fan is much better than no fan, any performance loss / reduction in mpg is bugger all and should not be noticable.

J>i take it that its knackered, as when i start the engine from cold, or

i would be happy to leave the seized one on long term, but it looks to have a slight bend in the coupling, and viscous bit is all damaged/dented. after the hastle i have had recently with the water pump and other bits, i don't want to risk shagging the new pump i have just fitted.

that said, i suppose =A360 spent now on a new one, will be better than knackering the new pump and having to replace and still need a fan??

Cheers anyhow.

Andy

A fixed fan could be using about 6hp at anything over 2500 erpm. A disengaged viscous unit will only use about 1hp. That 5hp has to come from fuel.

Huw

Which sounds about right. The viscous fan should however engage fully in hot weather, as we have had recently, if the engine has been working hard. It could occasionally engage also during prolonged town use but it would likely cycle itself more often.

It is surprising that viscous fans do not engage more often than they do in general.

Huw

i don't think i explained too well, the fan seem to not be pulling any air through, what ever the temperature of the engine or amount of revs.

If the instrument panel water temperature gauge does not venture above about the 3/4 mark then what's the problem? If it hits red or the water boils over, *then* you have a problem and not really before.

Huw

Mine's the same. I think yours is normal and I would leave well alone, taking note of the post above mine. TonyB

yes now i have the fixed/seized fan on, it sits happily (as huw stsded) at around the 3/4 mark, with the other fan on, up to, and into the red :-(

Andy

That's the whole point of a viscous fan, isn't it? ie: it shouldn't be blowing air until the engine gets hot.

I was helping a friend fit a 2.8 Daihatsu engine to his IIa Land Rover and got to playing with the viscous unit as I'd never seen one up close. It turned stiffly against the shaft for several turns then quickly loosened off until it seemed to be mounted on bearings with no viscosity at all. That, he assured me, was the correct action.

On or around Mon, 5 Sep 2005 20:16:07 +0100, "Huw" enlightened us thusly:

normally, I guess there's enough airflow and/or cooling. I've almost never had a correctly-working viscous fan cut in in normal use - I've known the one on the sierra do so when tuning the gas system, which involves running it at 3000 rpm with the vehicle stationary.

On or around 5 Sep 2005 14:30:02 -0700, "andy" enlightened us thusly:

chances are your rad is knackered. On the 110 with the V8 in it, I perpetually overheated when running slowly or under heavy load even with a fixed fan or running electric fan, until I gave up and replaced the rad, it then sat at half-gauge under almost any provocation.

I've never yet succeeded in unblocking a buggered rad, either - problem is that you can't shift enough water through it to clear all the tubes - once about a couple of dozen tubes are clear, the water flow through them and not the blocked ones. Anything violent enough to do the job chemically would probably eat the rad as well...

Edward II has similar trouble - rad looks iffy, so replacing it is on the to-do list.

In article , Badger writes

That's not the viscous thing per se, but poor control of the electric ones. They ought to be continuously variable speed, not just on-off ( which would indeed cause the thermal 'wobble' you mention).

Incidentally, the engine is more efficient at higher temperatures, so over-cooling is inefficient. Also the mechanical belt coupling to the fan soaks up a lot of power, which the electric ones don't.

I'm not saying I know for certain, but I don't think it's at all as clear cut as you're suggesting.

Regards,

Simonm.

True, but AFAIK none of the readily available electric kits have variable speed control, only some seriously overpriced motorsport stuff.

But the extra load on the significantly more thermally inefficient alternator soaks up the same or more power via its drive belt, so that doesn't really come into it.

The whole point is, the energy for the fan must come from somewhere, and whatever way you choose to do it, it comes from burning fuel in the engine, so cut out as many energy conversion processes as possible and reduce the ammount of energy lost at each process. This is a perfectly valid argument for a correctly operating viscous fan hub, when it is in unlocked (freewheel) mode, the power drain on the engine is next to nothing. Badger.